The smallest roadster in the automaker's lineup is all-new for 2012, and hardly in need of more power, but that hasn't stopped Mercedes-Benz from shoehorning its AMG-tuned 5.5-liter V8 under the hood. The naturally-aspirated M152 engine, featuring direct injection, is rated at 415 horsepower at 6,800 rpm with 398 pound-feet of torque at 4,500 rpm. The standard gearbox is AMG's Speedshift Plus 7G-Tronic automatic with three electronic modes. Rev-matching on downshifts is also standard. According